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Biomedical subjects

M Bhattacharjee

Publications and source records attributed to M Bhattacharjee.

At least 73 records · Page 4Linked to original sources
PubMed1994

Spontaneous thrombosis in a coronary artery fistula with aneurysmal dilatation of the sinus of Valsalva.

This case report describes spontaneous thrombosis of a congenital coronary artery fistula with associated aneurysmal dilatation of the right coronary sinus of Valsalva. The grossly dilated sinus of Valsalva was reconstructed with a Dacron patch. Coronary revascularization was performed with a sequential saphenous vein graft anastomosed to the right posterior descending and posterior ventricular arteries distally and to the aorta proximally.

Aged↗
PubMed1992

Protein purification using a soluble affinity matrix: purification of estrogen receptor with estradiol-polylysine conjugate.

A new strategy for protein purification using a soluble affinity matrix is described. The method was used for purification of estrogen receptor. Cytosols from rat uteri and human fibroid uterine tissue, after fractionation by ammonium sulfate, were treated with estradiol-polylysine conjugate. The highly basic affinity complex was separated from other proteins by DEAE-Sephacel chromatography. After dissociation of the eluted complex with excess estradiol, the receptor was recovered by CM-Sephadex chromatography. A 2000-fold purification of the rat uterine estrogen receptor was obtained with an activity recovery of 35%.

Animals↗
PubMed1992

Role of the origin of transfer in termination of strand transfer during bacterial conjugation.

Conjugal transfer of the broad-host-range plasmid R1162 is initiated and terminated at the nic site within the 38-bp origin of transfer (oriT). Termination involves ligation of the transferred single strand by the plasmid-encoded MobA protein. Several different assays were used to identify the oriT DNA required for termination. For plasmids containing two oriTs, with transfer initiated at one and terminated at the other, the inverted repeat within oriT is important for termination. Deletion of the outer arm reduces the termination frequency; those terminations that do occur probably depend upon nicking at this oriT prior to transfer. The locations of second-site suppressor mutations indicate that base pairing between the arms of the inverted repeat is important for termination. In vitro, the inverted repeat is not required for specific cleavage of single-stranded DNA at nic, but competition experiments indicate that oriTs with the inverted repeat are preferentially cleaved. We propose that the function of the oriT inverted repeat is to trap the plasmid-encoded MobA protein at the end of a round of strand transfer, thus ensuring that the protein is available for the ligation step.

Bacterial Proteins↗
PubMed1990

Binding of estradiol-peroxidase conjugate to estrogen receptor.

The binding of estradiol-horseradish peroxidase conjugate to rat uterine cytosolic estrogen receptor was studied. The conjugate having a steroid to enzyme ratio of 2.8:1 was allowed to bind to protamine precipitated receptor in presence or absence of 100-fold excess of free estradiol. The bound enzyme activity was measured and the data subjected to Scatchard analysis to obtain the dissociation constant and the number of binding sites. Although the binding parameter so obtained differed from values obtained using radiolabelled estradiol, the method may be used for comparative studies.

Animals↗
PubMed1990

Dissociation of gastric acid and pepsinogen secretion in response to mercaptomethylimidazole--a new secretory compound.

Mercaptomethylimidazole (MMI), a potent antithyroid drug of the thionamide group, induces both acid and pepsinogen secretion independently in control and pylorus ligated mice. The effect is dose dependent and the drug is more effective than histamine, carbachol or isoproterenol when administered by an intraperitoneal route. MMI-stimulated pepsinogen secretion could be dissociated from the acid secretion by the use of cimetidine and omeprazole which effectively block the acid secretion without affecting the pepsinogen output. Neither acid nor pepsinogen secretion by MMI is inhibited by atropine indicating a lack of muscarinic receptor involvement in both of the processes. Nifedipine and verapamil, the calcium antagonists, by inhibiting the MMI-induced acid secretion can also dissociate pepsinogen secretion from the acid secretion. Clonidine, an alpha 2-agonist, and hexobarbital, a membrane active barbiturate, also inhibit acid secretion without affecting the pepsinogen output. These data indicate that MMI induces pepsinogen secretion independent of acid secretion. Furthermore, MMI-stimulated acid secretion is not additive with that of the histamine indicating same site (H2-receptor) of action while its synergistic effect in presence of carbachol (muscarinic receptor) indicates different site of interaction of the two compounds. On the other hand, an additive effect of MMI and carbachol on pepsinogen secretion indicates that while the carbachol effect is mediated through the muscarinic receptor, MMI stimulates pepsinogen secretion through some still unknown mechanism.

Animals↗
PubMed1989

Histamine H2-receptor mediated stimulation of gastric acid secretion by mercaptomethylimidazole.

Intraperitoneal administration of mercaptomethylimidazole (methimazole), a potent antithyroid drug belonging to the thionamide group, caused a significant increase in gastric secretion both in control and pylorus-ligated mice. The drug also induced significant stimulation of gastric acid and pepsinogen secretion in both the animal systems studied. The dose-response curve indicated a nearly 10-fold increase in acid output by injection of 0.55 mg mercaptomethylimidazole per 25 g body weight. The duration profile of the drug response at the dose mentioned showed acid secretion almost at a linear rate up to 2.5 hr, after which the response decreased to some extent. Of the other antithyroid drugs of the same family, only thiourea activated acid secretion but the response was much smaller than mercaptomethylimidazole. Histamine, one of the physiological secretagogues of gastric acid secretion, was found to be less active than mercaptomethylimidazole. Mercaptomethylimidazole-induced stimulation of acid secretion could be effectively blocked by prior administration of cimetidine and completely by omeprazole and not by atropine. Verapamil and nifedipine had also some inhibitory effect. These observations indicate that mercaptomethylimidazole stimulates HCl secretion through the involvement of H2-receptor and through the functioning of the H+-K+-ATPase of the parietal cells. The bulk movement of water during increased HCl secretion was partially sensitive to cimetidine and omeprazole and was also associated with an increased secretion of Na+ and K+ in the gastric juice. This indicates that mercaptomethylimidazole also induced water transport through a separate mechanism.

Animals↗
PubMed1988

Thyroid hormone regulation of alpha-lactalbumin: differential glycosylation and messenger ribonucleic acid synthesis in mouse mammary glands.

Mouse mammary tissue, when cultured in the presence of insulin, corticoids, PRL, and physiological levels of T3, shows increased synthesis and secretion of alpha-lactalbumin. Tissue cultured in the presence of insulin, hydrocortisone, PRL, and T3 synthesizes two distinct forms of alpha-lactalbumin, but secretes only one form. Tissue cultured in the absence of T3 synthesizes and secretes only one form. To address the question of whether these two electrophoretically distinct forms arose by differential glycosylation of the same polypeptide or by synthesis of two different polypeptide precursor chains, mammary tissue was cultured in the presence of insulin, corticoids, and PRL with or without T3, and the mRNA and alpha-lactalbumins were isolated. Northern blot analyses indicated that mammary gland tissue cultured in the presence of T3 contained 2.46 times more alpha-lactalbumin mRNA than tissue cultured only in the presence of insulin, hydrocortisone, and PRL. This enhanced mRNA level was confirmed by in vitro translation experiments where tissue cultured in the presence of insulin, hydrocortisone, PRL, and T3 produced mRNA that resulted in 2.1 times as much radiolabeled alpha-lactalbumin as tissue cultured in the absence of T3. Sodium dodecyl sulfate-polyacrylamide gel analysis of the in vitro translation products revealed only one band, suggesting the presence of only one message. Endoglycosidase digestion of the two forms of alpha-lactalbumin produced in the presence of T3 resolved them into a single band on sodium dodecyl sulfate-polyacrylamide gels. Thus, the electrophoretic differences between the two forms synthesized in the presence of T3 appear to be due to differential N-linked glycosylation of the same polypeptide chain and not to synthesis of two different polypeptide precursor chains.

Aldosterone↗
PubMed1987

Milk protein synthesis by mammary glands of vitamin D-deficient mice.

Mammary glands from second generation vitamin D-deficient mice and rats were examined for their ability to make the major milk proteins, casein and alpha-lactalbumin, both in vivo and in vitro. The glands from the rachitic animals were morphologically indistinguishable from those of age-matched controls. When placed in explant culture, glands from vitamin D-deficient mice and rats underwent DNA synthesis at a rate comparable to that of glands from the vitamin D-replete controls. However, the hormonally induced synthesis of casein and alpha-lactalbumin was significantly reduced in explants of glands from rachitic vs. control animals. The reduction in casein-synthesizing ability by mouse mammary gland explants was not reversed by the addition of 10(-8) or 10(-6) M 1,25-dihydroxycholecalciferol to the culture medium, but could be reversed by pretreating the vitamin D-deficient mice with the D metabolite in vivo for 10 days before the onset of culture. The decrease in milk protein synthesis in culture is paralleled in vivo by a decrease in milk protein content in the milk and lactating mammary glands of vitamin D-deficient mice and rats. Both in vivo and in vitro, it is the two highest mol wt caseins that are most affected by the lack of vitamin D in the diet. These data suggest that vitamin D does not play a fundamental role in growth and morphological development of the normal mammary gland, but, rather, it is important in maintenance of full hormonally induced functional differentiation of the mature gland.

Animals↗
PubMed1985

Isolation, characterization, and regulation of the prolactin receptor.

The prolactin, or lactogenic hormone, receptor has been purified (approximately 80%) from lactating mouse liver and human term placenta by the nondenaturing zwitterionic detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate and a prolactin affinity column. The isolated "core-binding unit" has a molecular weight of 37,000 +/- 2,000 daltons. It retains the specificity for lactogenic hormones and binds prolactin with an affinity (Ka = 2 to 6 X 10(9) M-1) similar to that of the receptor as it occurs in its membranous environment (Ka = 3 to 5 X 10(9) M-1). Whether this "core-binding unit" exists on the cell surface in a cryptic or active form is influenced greatly by its association with other membrane proteins and the concentration of phosphatidylcholine within its local membranous environment.

Animals↗
PubMed1984

Thyroid hormones enhance the synthesis and secretion of alpha-lactalbumin by mouse mammary tissue in vitro.

The syntheses and secretion of casein and alpha-lactalbumin were examined in organ culture of midpregnancy mouse mammary glands using serum-free medium supplemented with various combinations of insulin, hydrocortisone, PRL, and L-T3. Using highly specific antibodies raised against mouse caseins and alpha-lactalbumin, we demonstrate a selective enhancement of alpha-lactalbumin and lactose synthesis and secretion when all four hormones are present in the culture medium. Production of casein was not modified by the presence of L-T3. Hydrocortisone at concentrations of 10(-9)-10(-6) M inhibited the secretion of both casein and alpha-lactalbumin into the culture medium. The addition of L-T3 to the medium selectively overcame the inhibition of alpha-lactalbumin secretion by hydrocortisone. Extracts of tissue cultured in the presence of L-T3 contained two distinct forms of alpha-lactalbumin, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the absence of L-T3, synthesis of a single form of alpha-lactalbumin prevailed. In the culture medium, predominantly one form of alpha-lactalbumin was detected regardless of the presence of L-T3 during culture. These data clearly indicate that thyroid hormones play an important regulatory role in functional differentiation of the mouse mammary gland.

Animals↗
PubMed1983

Purification and characterization of mouse alpha-lactalbumin from lactating mammary glands.

The whey protein, alpha-lactalbumin, was purified from lactating mammary glands of mice at high yields. It exists as two major charge forms (pI values of 6.2 and 5.8) with similar molecular weights (approx. 14600). Antibodies prepared against these peptides precipitate newly synthesized and secreted alpha-lactalbumin from organ cultures of mid-pregnancy mammary glands. The antibody is specific for mouse alpha-lactalbumin as it does not react with mouse casein, mouse serum or purified bovine alpha-lactalbumin or galactosyl transferase. In addition, it blocks enzymatic activity of alpha-lactalbumin in mouse milk but has no effect on guinea pig or human milk. A very sensitive radioimmunoassay has been developed with this antibody which can detect alpha-lactalbumin levels as low as 0.25 ng.

Animals↗